v3.1.15.0

Release 3.1.15.0 (Jul 1, 2026) -- compared to 3.1.14.1

• deepdata: Widen merge_deep_pixels srcpixel to int64_t, change its return type, and add OIIO_NODISCARD_ERROR. #5252 #5253 (by @luna-y-kim / Luna Kim)
• ImageBuf: Fix copy ctor of IC-backed ImageBuf zeroing bufspan strides. #5244
• cineon: More robust to invalid numbers of channels and bit depths; also fixes a channel-naming counter bug and a memory leak in init(). #5250 (3.1.15.0, 3.0.20.0)
• deepdata: Correct Zback channel in sort(), change int pixel to int64_t. #5241 (by @luna-y-kim / Luna Kim)
• fits: Fix stack overflow from recursive header-block reading on corrupt files; convert to an iterative loop with a 10000-header safety limit. #5248 (3.1.15.0, 3.0.20.0)
• fmath.h: Fix typo in convert_type default argument, min() should have been max(). #5227 (by @luna-y-kim / Luna Kim)
• hdr: Make the HDR reader tolerant to CR in the ASCII header. #5261
• iff: Fix allocation bug when reading 16 bit RGBA + float z (buffer size did not account for the z channel). #5251 (3.1.15.0, 3.0.20.0)
• tiff: The "tiff:half" hint was only applying to first MIP level. #5240
• ci: Fixes to build_opencolorio.bash script #5219; upgrade 'latest' CI tests to OpenEXR v3.4.14, fmt 12.2, PugiXML v1.16 #5245.
• build: Add support for gcc-15 #5126, gcc-16 #5225, and C++26 #5230, each tested in CI.
• build: Suppress warnings in fmt library when building on Mac. #5237 (by @antond-weta / Anton Dukhovnikov) (3.1.15.0, 3.0.20.0)
• int: Remove deprecated std::codecvt from strutil.cpp internals. #5107
• docs: Fix typos in fmath.h comments. #5222 (by @luna-y-kim / Luna Kim) (3.1.15.0, 3.0.20.0)
• docs: Fix typos and update reference link in deepdata comments. #5238 (by @luna-y-kim / Luna Kim)
• docs: Clarify plugin.h explanations by saying their Unix-like equivalents. #5226
• docs: Fix typo in bitcast docs. #5255